Correctly combining a two layer material in cycles
This link might be helpful. It has a cycles material that has thin film interference. Here is a Wikipedia article on what thin-film interference is.

Excerpt:


  Thin-film interference is a natural phenomenon in which light waves
  reflected by the upper and lower boundaries of a thin film interfere
  with one another, either enhancing or reducing the reflected light.
  When the thickness of the film is an odd multiple of one
  quarter-wavelength of the light on it, the reflected waves from both
  surfaces interfere to cancel each other. Since the wave cannot be
  reflected, it is completely transmitted instead. When the thickness is
  a multiple of a half-wavelength of the light, the two reflected waves
  reinforce each other, increasing the reflection and reducing the
  transmission.


Here is the blender file download link. I think it can be applied to what you want. It puts a bit of "thickness" on your object. If you want it to be more dramatic/visible, let me know and I'll try to brainstorm another solution.